An engine starting and charging device comprising a starting motor and a charging generator as one unit has been suggested as a prior art, for example, one disclosed in Laid-Open Japanese Pat. No. Sho No. 61-54949.
FIG. 1 is a sectional view of a prior-art engine starting and charging device disclosed in Laid-Open Japanese Pat. No. Sho No. 61-54949. In FIG. 1, a starting and charging device body 1 comprises revolving-field poles 2a, 2b, a field coil 3, an armature core 4, an armature coil 5, and a crank angle detector 6 as major components.
The revolving field poles 2a, 2b are a pair of comb-shaped field poles produced of a ferromagnetic material, which are coupled as a unit through a ring 7 of non-magnetic material such that those magnetic pole sections are disposed alternately in the circumferential direction.
The revolving-field pole 2a functions also as a flywheel, is fitted on an engine crankshaft 8, and then securely installed by a bolt 9 on the shaft end of this crankshaft 8.
In the side portion of the revolving-field pole 2a is formed a cutout 10 which, combined with the crank angle detector 6, is used to detect the crank angle. The same number of cutouts as the number of the revolving-field poles 2a are provided at equal intervals on the circumference.
The width of the cutout 10 in the circumferential direction makes an angle equal to about one half of 360 degrees divided by the number of the cutouts.
The revolving-field poles 2a, 2b described above are so designed as to be excited by the field winding 3. This field winding 3 is mounted on the field core 11.
This field core 11 is secured by bolts not illustrated, to a rear plate 12, facing the revolving-field pole 2a across a slight gap a provided in the axial direction, and the revolving-field pole 2b across a slight gap b.
The field winding 3 is provided on the fixed side, dispensing with a collector ring; however, because the current flowing into the field winding 3 is much less than the current of the armature winding 5, the current can be applied also through a collector ring and brushes.
The armature core 4 is formed by laminating silicon steel sheets, within the inner periphery of which are provided a large number of slots for setting the armature coil 5 therein. The armature coil 5 is of a three-phase distributed winding type as a common commutatorless motor.
The armature core 4 is fitted to a mounting frame 13, positioned and locked from turning by a key not illustrated, to this mounting frame 13. At this time, the armature core 4 is fixed by a spacer 14 in the axial direction relative to the mounting frame 13 through a spring ring 15.
Furthermore, the mounting frame 13 is mounted by a bolt 16 to the rear plate 12. The rear plate 12 is mounted to the engine body which is not illustrated.
In the meantime, the aforementioned crank angle detector 6 serves as a signal source to energize an armature current switching circuit; here are used signal-generating type proximity switches.
The proximity switches are mounted on the rear plate 12 such that their detecting elements will face each other on the circumferential line where the cutouts 10 of the revolving-field pole 2a are provided, and output a binary signal "1" or "0" corresponding to the crank angle (field pole position) as signal generating conditions vary with a change in inductance at the cutout and non-cutout sections of the revolving-field pole 2a. When a three-phase armature winding 5 is employed, there are used three crank angle detectors 6.
A clutch 17 functions to interruptedly transmit the power from the crankshaft 8 to the transmission drive shaft 18. This clutch 17 is a diaphragm spring clutch comprising a clutch disc 19, a pressure plate 20, a diaphragm spring (disc spring) 21, wire-rings 22, 23, and a clutch cover 24.
The clutch cover 24 is mounted by bolts 25 to the revolving-field pole 2a which serves also as a flywheel. Numerals 26a, 26b are clutch discs.
Next, operation at the time of starting will be explained. When a key switch (not illustrated) is turned to the START position with the engine left stationary, the current will flow from a battery (not illustrated) into the field winding 3 and the armature winding 5, thereby producing a torque at the revolving-field poles 2a, 2b to turn the crankshaft 8 which is directly coupled therewith.
When the revolving-field poles start turning, the crank angle detector 6 will detect the positions of these revolving-field poles, thus operating the armature current switching circuit (not illustrated) such that the speed of the revolving field which is formed by the armature winding 5 will become the same as the speed of rotation of the revolving-field poles; and accordingly the revolving-field poles 2a, 2b, gaining a torque, will further accelerate.
Since a great starting torque is obtainable on account of such a positive feedback action, the engine will be started in a short period of time by the direct-coupled drive.
Subsequently, after the engine has started, when the key switch is placed in the IGNITION position, the starting and charging device body 1 operates as an a.c. generator; the power generated thereby is converted into a d.c. power by a diode (not illustrated), being supplied to the battery and electrical equipment on the motor vehicle.
The operation of the clutch 17 is as follows. When the clutch pedal (not illustrated) is not depressed, the tension of the diaphragm spring 21, as well known, is applied by leverage to the clutch disc 19 mounted on the transmission drive shaft 18 through a pressure plate 20. This clutch disc 19, therefore, is pressed against the side of the revolving-field pole 2a, thus connecting the clutch 17.
When the clutch pedal is depressed, a sleeve which is not illustrated will slide in the axial direction, pressing the central part of the diaphragm spring 21 in the direction of the arrow C. This diaphragm spring 21 will deflect back on the wire rings 22, 23 as a fulcrum, thereby removing the pressure applied to the clutch disc 19 and accordingly disconnecting the clutch 17. Thus the transmission of power from the crankshaft 8 to the transmission drive shaft 18 will be interrupted.
As described above, the starting and charging device body 1 is formed integral with the clutch 17 by directly coupling the revolving-field pole 2a of the starting and charging device body 1 with the engine crankshaft and further by using this revolving-field pole 2a as a carrier of the clutch 17 for connection and disconnection between the crankshaft 8 and the transmission drive shaft 18.
In the prior-art engine starting and charging device described above, the whole body of the device is hermetically enclosed and therefore the atmospheric temperature of the hermetically enclosed chamber will become very high on account of a great deal of frictional heat occurring at the time of connection and disconnection of the clutch disc 19 of the clutch 17, and a resistance loss heat resulting from the flow of tremendous current into the armature winding 5 or the current flowing into the field winding 3.
However, there is a problem that, since there is provided no cooling means such as a cooling fan, and if a cooling means is provided, a cooling effect will be low in the hermetically enclosed chamber, resulting in excessively high temperature rise at each part, deteriorated quality in respect of heat resistance, decreased current in the field winding 3 in respect of performance, and accordingly in a failure in obtaining a desired starting torque or output current.
In the meantime, the clutch plate requires to be produced of a material having a great frictional coefficient and high wear resistance, but, on the contrary, the revolving-field poles 2a, 2b which constitute the magnetic poles require to be made of a low wear-resistant material such as S10C of high permeability.
Therefore, still another problem, beside the aforesaid problems, is that the temperature of the revolving-field pole 2a rises in excess because of the frictional connection of the clutch plate, with the result that the revolving-field poles will be subjected to deformation and damage.
Furthermore, still another problem is that since the clutch 17 is directly mounted to the revolving-field pole 2a, vibration caused by clutch connection and disconnection passes to this revolving-field pole 2a.